The propagation of inverted Neel wall sections in a serial access memory system was first proposed by L. J. Schwee in the publication "Proposal On Cross-Tie Wall and Bloch Line Propagation In Thin Magnetic Films", IEEE Transactions On Magnetics, MAG 8, No. 3, pp. 405-407, September 1972. Such a memory system utilizes a ferromagnetic film of 81% Ni19% Fe of approximately 300 Angstroms (A) thickness in which cross-tie walls can be changed to Neel walls and Neel walls can be changed to cross-tie walls by applying appropriate fields. Associated with the cross-tie wall is a section of inverted Neel wall that is bounded by a cross-tie on one end and a Bloch-line on the other end.
In such cross-tie wall memory system, information is entered at one end of the serial access memory system by the generation of an inverted Neel wall section bounded by a cross-tie on one side and a Bloch-line on the other, which is representative of a stored binary 1, and a non-inverted Neel wall section (i.e., the absence of a cross-tie and Bloch-line pair), which is representative of a stored binary 0 and is moved or propagated along the cross-tie walls by the successive generation (and then the selective annihilation) of inverted Neel wall sections at successive memory cells along the cross-tie wall. In the D. S. Lo, et al, U.S. Pat. No. 3,906,466 there is disclosed a propagation circuit for the transfer of inverted Neel wall sections at successive memory cells along the cross-tie wall. In the L. J. Schwee U.S. Pat. No. 3,868,660 and in a Naval Ordnance Laboratory Report NOLTR 73-185, Oct. 1, 1973, L. J. Schwee, et al, there have been published some recent results of the further development of cross-tie wall memory systems and of detectors for the readout of the binary information that is stored therein.
In the copending patent application of E. J. Torok, et al, Ser. No. 608,437 filed Aug. 8, 1975, now U.S. Pat. No. 4,034,359, disclosed a novel method of and a configuration for reading out the information that is stored in the magnetizable layer of a cross-tie wall memory system. The novel configuration includes: conductively coupling a conductive pillar to the magnetizable layer at or near the Bloch-line position in the memory segment of the cross-tie wall; conductively coupling to the magnetizable layer, concentric to the pillar, a conductive ring; coupling an electrical signal across the pillar and ring; and, determining the resistance in the magnetizable layer between the pillar and ring as an indication of whether or not a Bloch-line in stored in the memory segment. In this prior art configuration, because of the use of a concentric ring and a small diameter pillar, several deposition steps are required as a very small hole must be formed in an insulating layer. A deposited conductor is required to couple the pillar to an external lead for the readout function, which deposited conductor must pass over the concentric ring, separated from it by an insulative layer, and the superposed portion of the deposited conductor. The deposited conductor can possibly be electrically shorted to the ring such that considerable degradation of the readout signal may be experienced. The present invention is directed toward an improvement in such prior art configuration in which a probe and a concentric crescent are deposited directly upon the magnetizable layer during the same deposition step while further obviating the necessity of the deposited conductor and special insulating layer and their possible adverse affects upon system operation.